Intermediate
Technical
In the Industry Vocabulary Test
clonus
Pronunciation: CLO-nus
Rhythmic muscle contractions triggered by sudden stretch, indicating upper motor neuron lesion.
Full Definition
A series of involuntary, rhythmic muscle contractions that occur in response to sudden passive stretching of a muscle or tendon. Clonus indicates damage to upper motor neurons and is commonly tested at the ankle (ankle clonus) or patella (patellar clonus). The rhythmic contractions typically occur at a frequency of 5-8 Hz and may be sustained or transient.
Usage
Usage note: Sustained clonus (>5 beats) is more clinically significant than transient clonus.
In Context
- "Sustained ankle clonus was elicited bilaterally during the neurological examination." — Clinical assessment
- "The presence of clonus confirmed upper motor neuron involvement in the spinal cord lesion." — Diagnostic evaluation
Also known as
rhythmic contractions
Contrasted with
absent clonus
Don't confuse with
tremor
fasciculation